Production of electrical energy variations



LEM?

Fak, 89 E92?,

, C. G. SMITH PRODUCTION 0E ELECTRICAL. ENERGY vERIAEIoNs.

Original Filed oct. 2o, 1920 asians l-sica.

- l'CHARLES G. SMITH,v or rinnronn, MASSACHUSETTS, ASSIGNOE,I BY MESNEASSIGN- MENTS, To RAYTHEON MANUFACTURING columnar; @cameraman/MASSACHU-SETTS; A CORPORATION OE-MASSAOHUSETTS.

rnonUoTioN OE ELEcTnrcAL ENERGY VARIATIONS,

Application led October 20, 1920, Serial No. 418,263. Renewed December2, 1926.

The present invention relates to anapparatus for producing energyvariations in electrical circuits.

This invention is invention disclosed by me in an application filedAugust 30, 1920, Serial No. 406,886.

This application discloses the use of electrodes immersed in a gas andlspaced in close proximity to normally prevent electric dischargethrough the gas even when subjected to a high potential gradient.- Thisinsulating property of the gap is secured by locating the activesurfaces of the 'electrodes'sub jected to such a potential gradient adistance apart which is of the order of magnitude of the mean free pathof thev electrous', thus avoiding aI4 sufficient number of collisionsbetween electrons and atoms to ,initiate gaseous conduction.

' A gap or Jtube of the above described character will conduct freelywith alrelatively small voltage drop between electrodes if a magneticeld of proper value is interposed between the electrodes. pressedvoltage is increased to a -certain critical or shut off value, however,the tube vrefuses to conduct and suddenly becomes insulating. ByembodyingI the tube in a circuit including' properly designed inductanceand capacity" together with means for generating a voltage higherA thanthe voltage at which the tube will normally conduct, oscillatorycurrents may be generated, the frequency ofwhi'ch is determinedprimarily by the values ofl the inductance and capacity in the circuit.With this form of circuit arrangement, oscillations at substantially alldesirable frequencies may be produced, the gap or tube serving totransform the energy derived from the source of potential into energy ofoscillation.

An essential feature of the present invention then is the use of'a tubeof the character described which has the property o conducting currentfre-ely at a certain imv pressed voltage but which suddenly becomesinsulating when the impressed voltage is increased to a critical value.

A further feature of the invention consists in thelembodime'nt of a tubeof the character described in an electrical circuit including inductanceand capacity together with means for impressing upon the tube avoltbased upon a preceding If the irrif relatively and presents a newand efficient method of generating high frequency oscillations.

In the preferred embodiment of the invention the magnetic ield Strengthis such as to cause the tube to normally conduct current freely in onedirection and to insulate against the potential difference in theopposite direction.

In the accompanying drawings illustrating the preferred form of theinvention Fig. 1 represents a section in elevation of one form of tubewhich may be em loyed in conjunction with an appropriate clrcui-t forgenerating electrical oscillations, and Fig. 2 represents a typicaloscillatory, circuit with the tube embodied therein.

In the illustrated embodiment of the invention a tube of the characterVdescribed in my, copending application hereinbefore referred to isindicated at 10 and is provided With means 'indicated at 11 for creat--lwhere gaseous conduction takes place. This tube is embodied in a circuit13 which in cludes a generator 14 capable of delivering aboutfour-tenths of an ampere at 1500 volts. Also included in the circuit isa large inductance 1G in series with the tube and a small capacity 18shunted about the inductance.

tance and capacity already described an additional capacity 20 isconnected across In addition to the induek the circuit, as indicated, toprovide a path I for the flow of current when the tube shuts off uponreaching the critical voltage. The current from the generator ismaintained substantially constant and high frequency oscillations areprevented? from flowing causes a rising voltage across the tube.

f `tude and it Will'be seen that after a frac-7 be sutliciently low toagain permit of gaseous three hundred volts. This impressed volt# agerises. at av rate determined largely by the inductance 16 until thecritical, voltage is reached, at which the tube suddenly refuses toconduct further current and becomes insulating. Upon this suddentransformation of the tube' from a conducting to an insulating state,the energy already stored up in the inductance 16 cau'ses current toflow through the capacity 18, charging the latter to a high potential.|The` inductance 16 and capacity 18 together act as a resonant circuit-which, when isolated from the re- `mainder of the system by theinsulating property of tube 10, is free to electrically .oscillate inthe usual manner, that is, the energy of the oscillating circuit isfirst stored up as electrostatic energy in the condenser and next aselectromagnetic energy. in the induotance. During the Oscillationl thepotential difference across the inductance 16 lundergoes a sinusoidalvariation in amplition of a cycle, the potential difference between theelectrodes of tube 10,v as determined by the voltage ofthe generator 14and the voltage across the vinductance 16, will conduction, andthe cycleproceeds as before. rThe tube 10 therefore acts as an automaticl feedingdevice, vits purpose being to periodically feed energy into the resonantcircuit 16, 18 and sustain t-he oscillations. The frequency of theoscillations is determined by the relativevalues of inductancefl andcapacity 18. y'llhese .oscillations may be Iutilized in any suitablemanner,A as for example by a load circuit indicated at 26 which isinductively coupled with the circuit 13,

as` shown in Fig. 2. y

With this type of circuit and a direct current generator deliveringapproximately four-tenths of an ampere at 1500 volts frequenciesdetermined principally by the natural period of the circuit 16', 18 andranging from 10 cycles to 100,000 cycles per second have been produced.The critical voltage at which the tube becomes insulat- 1mg variesapproximately as the square of the magneticI eld strength applied to thetube and may accordingly be varied by'suitable variations in thestrength of this field.

The tube actually employed for the purpose of generating oscillations isconstructed ,substantlally as described in a `copendingapplicationlfiled by me for a rectifier. This termas' tube consists `ofa sealed enclosing vessel 30 y containing concentric cylindricalelectrodes 31 and 32 constructed of non-magnetic material, such asmolybdenum. Conduction takes place in the' region separating theopposite surfaces of the two electrodes which are under a-potentialgradient and these suifaces are located in suiiiciently close proximityto normally prevent gaseous conduction through the space separatingrthem, even under excessively high potentials. A magnetic ield with thelines of force ex.- tending "substantially parallel to the axis of theelectrodes maybe'created by ya perma,v

nent magnet 34 located with respect to the tube, as shown'in thedrawings. Thecritical voltage at which thel tube becomes insulating maybe conveniently varied by adjusting the magnetic field. rlfhisadjustment of the magnetic field 'may be most readily carried out bymovingtthe permanent magnet 34 toward or yaway from the receptacle 30.Cooperating with theA permanent magnet are tubes or cylinders 37 and 38of Vmagnetic material which engage with opposite ends of the electrodelcylinder 32. These. cylinders are connected to the electrode 32 and toone another by a sleeve 39 of copper or similar non-magnetic material.lt will be observed that the outer electrode 32 con-` sists of a thinmetallic cylinder having its opposite ends received in igrooves formedin the adjacent faces of the cylinders 37 and 38. lin order to permitthe 4free escape of y heat from the regionsurrounding the out-erelectrode 32, the connector sleeve 39 is preferably provided withopenings or .slots 44,

as indicated in the drawings. The inner electrode 31 isconnected at itsopposite ends with iron rods 45 and 46, the rod 46 having a head 48formed thereon and the rod 45 having its end threaded at 49. Theelectrode ispreferablyfused or welded to the rods tol form a continuousrod having its central section of 'non-magnetic material, as

indicated: Surrounding the outer ends of therods 45 Jand 46 areinsulatingcylinders 50 and 51 of glass or similar material which yareseated in recesses 52 formed respectivelyl in the cylinders 37 and 38.rllhe insulating ycylinders may be 'held' in place by collars 54 and 55of copper or other non-magnetic material, each having a neck 56 whichnprojects into the space between therodsand the sun rounding insulatorcylinders 50- and 51. The several elements are -retained in as'-se'mbled relation through the provision of aY nut 58 engaging with thethreadedend 49 and serving to draw thecollars 54 andlSfl against theendspof the cylinders 50 and 51.

1n -order to insure that all paths through the supporting dielectricsubjected to a potential gradient shall be long and that 'all pathsthrough the gas shall. be short, the outer-ends of the cylinders 37cand38 are eounterbored lat'60 to separate the point of contact between themagnetic and insulating cylinders a substantial distance from thecollars 54 and -55 which are in contact with the central electrode rod;In addition the collars are each. provided with an annular flangeGQeXtending .parallel but spaced away from the walls of the enclosingvessel. From an inspection of the drawings it will be observed that theouter cylinders do not contact directly with the enclosing vessel butare centered within the vessel and spaced' away from the walls byspacing rings.y or washers 65. .One of the leading-in wires 66 may beconveniently connected with the head 48, passing'outwardly through theend of the tube and the other wire 67 may be con' nected with the sleeve39, passing outwardly through the side'of the tube at 68.v

It is preferred to employ helium as the medium within the tube throughwhich gaseous conduction takes place, the small and light moleculeofthis gas resulting in cer# tain distinct advantages.- In the first placethe small'molecules of helium have a rela` tively long mean free path atany given pressure, making it practical to employ higher gaspressurethan could be employed with a 4 gas having larger molecules.Furthermore the light weight of the molecules enables the 'tube tochange state from a conducting to an insulating medium and vice versamore 4 rapidly than it could if a heavierggas were employed.

The theory -upon which this l f critical voltage is'reached is believed,to be substantially as follows: By properlyv locating and positioningtwo electrodes within a gasfilled receptacle, as described in mycopending application, gaseous conduction between the surfaces oftheelectrodes is prevented, even, when 'these' electrodes are subjected toexceedingly high potentials. This isl due to thefact that thedistanc'eseparating the activesurfaces of the `elec'- trodes is shortA and of theorder of magni tude of the mean free path of the electrons.

" Owing to the short distancel which the ele ctrons travel, therefore,in passing from one electrode to the other, there is insufficient n tubesuddenly shuts off the lflow of current when a:

- mei-sed in a owing to the 'fact that the tube has a rising currentlvoltage characteristic.

This higher i voltage tends to straighten -out the curved. paths of theelectrons urvitil 'a point isl reached at which these paths'again becomeso short as to prevent substantial ionization,

thereby stopping gaseous conduction, and,

the tube suddenly becomes insulating' and so remains until' the applied.voltage lowered below the critical point.

From the foregoing-it ,will be 'evident that this oscillator is uniqueinthat the 1 characteristic curve (current abscissae and potentialordinates) of the gaseous conduction device'is discontinuous and thatthe current abruptlydrops in response to va change in the ionizationphenomenon accompanying the current flow without vary* ing the magneticfield or other conditions of the gaseous discharge space except as af'fected by the rcurrent in said space and the potential across'thespacelclaim-v i 1i. An electrical apparatus comprising a circuitincluding inductance and capacity and a generator of electricalpotential, and means embodied lin the circuit for conducting. current atpotentials less than the normal potential of the generator constructedand arranged to insulate against the con-,Y

duction of current when a critical potential is reached less than thepotential normally impressed by the generator' but greater than thepotential-at which conduction initially takes place. L f

-2. An electrical apparatus com-prisinga circuit including Linductanceand capacity and a source of potential, two electrodes imT as andconstructed and arranged to initlally permit a flowof currenttherebetween when the circuit is closed and to insulate, in response toincrease of the `current against a. further flow of current when acritical potential differencebetween the electrodes is reachedless thanVthe potential normallygcnerated in the circuit.

3; An'electrical apparatus comprising a plurality of electrodes immersedin a gas and spaced in suliiciently'close proximity to normally preventgaseous conduction, 'a

magnetic field interposed lin the space between the electrodes torender" the gap con ducting at certain potentials, and means forimpressing a potential upon the gap-greater than that at which the l,gapwill normally conduct to cause the gap to insulate at a certain criticalvoltage.

1..An electrical apparatus comprising a plurality ofelectrodes immersedin agas, al

gapy conducting at certain'potentials, and means for impressingaKpotential upon the gap greater than the potential at which the gapI wlllnormally conduct to cause thel v magnetic field interposed in the spacebe-v tween the electrodes of avalue to render the gap to insulate when acritical voltage is reached.

5. `An electrical apparatus comprising two electrodes immersed inagasand having i their surfaces located in suiiiciently close posing aconstant magnetic field in the region between the electrodes to causegaseous conduction below certain potentials, and means for impressingbetween the electrodes a potentialA difference greater than that atwhich the tube will conduct. l7. An electrical apparatus comprising acircuit having-a source of constant potential and providedwithinductance and capacity,

electrodes immersed in a gas and having 'their active' surfaces locatedin suiiiciently close proximity to normally render gaseous ionizationimpossible, andy a lmagnetic field interposed-'in 'the region separatingthe surfaces to normally cause gaseous' conduction at potentials lessthan the potential normally generated in the circuit.

8. An electrical apparatus comprising, two electrodes immersed in a gasand having their active surfaces separated a distance 40 `approximatingthe mean freepath of the electrons, a magnetic lield of substantiallyconstant strength *interposed in the region .separating the surfaces, acircuit including lthe two electrodes and including a source ofpotential greater than that at .which the tube will normally conduct,and an( inductance and capacity included in the cir? cuit andoscillation .of the circuit. 9i An electrical system comprising' aresonant circuit, a gaseousmedium, means to cause the gaseous medium tofreelyconl-ductat Avoltages below a certain critical value1 and tosuddenly change to an insulating. state for. lvoltages above thecritical Value, and means .for impressing upon the vgaseous'reg'ion arising voltage which starts l ata value less than the' critical voltageandincreases to avalue above the critical voltage. IO. An electricalsystem" comprising a resonant circuit, a gaseous medium having onedimension of the order of magnitude of the mean .free path ofI electronsin the means for' lenJ hening the paths of electrons inthe gas, an-means for impressing a rising ses adapted to determine the period ofmally permit of gaseous ionization, means `adapted toelectricallyconduct at low voltpotential `anda gaseous conductingdevice, and means producing ay current voltage.`

malaise electric field in the small dimension of the gaseous region tocause .the` lgaseous region to suddenly change from a conducting to aninsulating state.

1l. A system for generating electrical oscillations comprising aresonant circuit, two electrodes immersed in ay gas and spaced apart adistance which is too short to norl for lengthening electron paths inthev gas, 75 and means for impressing a rising potential differencebetween the electrodes to allow the gaseous medium to `feed energy intothe resonant circuit lfor vol-tages below a critical value and tosuddenly become insulating for all voltages above the critical value.

l2. Anfelectrical system comprising a circuit including indictance andcapacity, a pair of electrodes immersed in a gas and spaced apart adistance which is too short to normally permit of gaseous ionization,means for causing the gaseous medium to become conducting at lowvoltages, and means for impressing an increasing potential differenceAbetween the electrodes to cause the gaseous medium to suddenly change toan insulating st ate above a critical potentialv difference.

1 3. An electr-ical system comprising a circuit including inductance andcapacity, a gaseous medium having one dimension coinparable in magnitudeto the length of the mean free path of 4electrons in the gas and ages,and means for' impressing an increas-` 100 ingpotential difference uponthe gaseous region in a manner ,to cause electrons to traverse paths ofdecreasingl length across the small dimension of the gaseous medium,whereby the gaseous medium is caused to change to an insulating stateabove a vcritical voltage. 14.- An electrical oscillator comprisingaiwoscillating circuit connected to a source of relation which changesabruptly in response to .increase of current flow in the device, wherebythe ncurrent'abruptly drops when increased to a 'critical' value.

. 15. An electrical oscillator comprising an oscillating circuitconnected to a source of `)otential and a asous conductinvdevice ohaving means alo'rdin a characteristlc curve which retrogressesabruptly'at a'critil2@ cal point in response' to increase of current itherethrough. k l W.

' 16. 'An electrical oscillator comprising an oscillating circuitconnected to a source of potential andy a gaseous conducting devicehaving meansaflording a substantially-fdis- `continuous characteristiccurve sol that the currentsubstantially stops 4at a predeter mined pointof increase solely in'response to increase of current.

17. An' electrical oscillator comprising an oscillating circuitconnected to a source of potential and a gaseous conduction devicehaving spaced electrodes between which current may flow by -gaseousionization phenomena, characterized in that the spacing between theelectrodes and the gas pressure are correlated to produce a gaseousdischarge path in which t-he ionization 'phenomenon changes abruptly inresponse to increase `of current, whereby the flow of current by gaseousionization drops abruptly at a predetermined point of current increase.

18. An electrical oscillator comprising an oscillating circuit connectedto a source of potential anda gaseous conduction device having spacedelectrodes between which current may flow by gaseous ionizationphenomena, characterized in that the space between the electrodes isrestricted and conditioned to produce a gaseous path in which theionization phenomenon changes abruptly in response to increase olcurrent, whereby the iiow of current by gaseous ionization dropsabruptly at a predetermined point of `current increase.

19. An electrical oscillator comprising a gaseous conduction devicehaving spaced electrodes between which current may flow by gaseousionization phenomena, characterized in. that the spacing between theelectrodes and the gas pressure are correlated to produce a gaseousdischarge path in which the ionization phenomenon changes abruptly inresponse to increase of current, whereby the flow of current by gaseousionization drops abruptly at a predetermined point of current increase.

20. In an electrical oscillator comprising dischargean oscillatingcircuit connected to a source of potential and a gaseous conductiondevice havingr spaced electrodes between which current may flow bygaseous ionization phenomena, the method of producing oscillations whichcomprises confining the cunrrent path through the gas to a restrictedIspace andconditioningv the space abruptly to become substantiallynon-conducting-pon increase ot current iow to a pre eterlmined value inresponse to a change in the gaseous ionizatlon phenomena accompanyingthe current flow.

21. In an electrical oscillator comprising an oscillating circuitconnected to a source of potential and a gaseous conduction devicehaving spaced electrodes between which current may How by gaseousionization phe-,

nomena, the method of producing oscillations which comprises confiningthe current path through the gas to a' restricted space and conditioningthe space abruptly to become substantially non-conducting upon increaseof current flow to 'a predetermined value in response to echange-in thegaseous ionization phenomena accompanying the -current "flow, whilemaintaining substantially constant the conditions of said space exceptas affected lby the current -in said space and the potential across thespace.

22. An electrical oscillator comprising an oscillating circuit connectedto av source of potential and a gaseous conducting device having meansaffording a characteristic curve which abruptly changes, toward 'zerocurrent value, at a critical potential value, in response to increase ofcurrent therethrough.

CHARLES G. SMITH.

